Light guide, light source device, and image reading device

ABSTRACT

A light guide includes a first exit portion emitting first exiting light, a second exit portion emitting second exiting light in a different direction than the first exiting light, and a reflecting portion reflecting light entering the light guide to each of the first and second exit portions. The first and second exit portions respectively have first and second curved surfaces each having a convex cross section perpendicular to the long axis direction. The second exit portion is connected to the first exit portion in the direction perpendicular to the long axis direction. The reflecting portion is provided, in a plane facing the first exit portion and the second exit portion, at a position shifted in the direction perpendicular to the long axis direction from a position where a normal to the plane passes through a connection portion between the first and second exit portions.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/251,219, filed Aug. 30, 2016, which is a divisional of U.S.application Ser. No. 14/651,309 (now U.S. Pat. No. 9,841,549, filed Jun.11, 2015. U.S. application Ser. No. 14/651,309 is a national stage ofInternational Application No. PCT/JP2013/083508, filed Dec. 13, 2013,and claims the benefit of priority based on Japanese Patent ApplicationNo. 2012-278410, filed on Dec. 20, 2012, and Japanese Patent ApplicationNo. 2013-045671, filed on Mar. 7, 2013, the entire disclosure of whichis incorporated by reference herein.

TECHNICAL FIELD

The present disclosure relates to a light guide for emitting light intwo directions, a light source device using the light guide, and animage reading device using the light guide.

BACKGROUND ART

Light source devices for use in image reading devices and the like areused in facsimile machines, multifunctional devices, or devices forreading valuable papers and the like. Such an image reading deviceirradiates a document or paper to be read with light from a light sourcedevice in multiple directions. Light reflected by or transmitted throughsuch an object to be read is imaged by the image reading device throughan imaging element such as a lens and a mirror onto a photoelectricconversion element such as a complementary metal-oxide semiconductor(CMOS) sensor and a charge-coupled device (CCD) sensor to detect opticalinformation of the object to be read. The image reading device utilizesthe obtained image information for copying of documents, authenticitycheck of paper currency, check of level of degradation due todistribution, or the like. The reduced size of image reading devices andincreased reading speed in recent years require that the light sourcedevices become miniaturized and highly efficient.

Some conventional light source devices requiring such irradiation inmultiple directions are as follows. For example, Patent Literature 1describes an image reading device that irradiates an object to be readwith light in multiple directions using a single light guide and amirror.

Patent Literature 2 discloses a bifurcated light guide obtained from asingle light guide by disposing light diverting surfaces in multiplepositions of the single light guide in such a way that the verticalplanes extending in the longitudinal direction of the light divertingsurfaces intersect (see FIG. 2). Patent Literature 2 also discloses alight guide having one light diverting surface and two exit portions(portions having faces from which light exits) (see FIG. 10).

Patent Literature 3 discloses a light source device used for documentreading, the light source device including a linear light source, arod-shaped lens arranged in parallel to the linear light source, and alinear reflector arranged, at the opposite side of the rod-shaped lensfrom the linear light source, in parallel to the rod-shaped lens at aposition to intersect a second optical axis plane of the rod-shapedlens. The rod-shaped lens has a first optical axis plane containingoptical axes passing through a first linear focal point group containingfirst focal points and a second optical axis plane containing opticalaxes passing through a second linear focal point group containing secondfocal points. The first linear focal point group and the second linearfocal point group are located in the vicinity of the position where thesecond optical axis plane of light reflected by the linear reflectorintersects the first optical axis plane.

CITATION LIST Patent Literature

Patent Literature 1: Unexamined Japanese Patent Application KokaiPublication No. 2008-219244

Patent Literature 2: Unexamined Japanese Patent Application KokaiPublication No. 2008-216409

Patent Literature 3: Japanese Patent No. 5087337

SUMMARY OF INVENTION Technical Problem

However, both of the light guides disclosed in Patent Literatures 1 and2 are arranged so that the light diverting surfaces of the light guidesintersect, thus causing difficulty due to complicated manufacturingprocesses.

In the light guide disclosed in Patent Literature 2, the light divertingsurface is arranged over the entire surface, as illustrated in FIG. 10of Patent Literature 2. There is thus a problem of occurrence of lightexiting from the boundary area between the exit portions 5a and 5b, thatis, stray light exiting in a direction other than the intendeddirections. In addition, the smaller cross section of the light guidereduces the size of an entry surface 2, thus causing a problem of poormatching with a high brightness light source having a large lightemitting surface.

In the light source device used for document reading disclosed in PatentLiterature 3, the first and second linear focal point groups are locatedin the vicinity of the position where the second optical axis plane oflight reflected by the linear reflector intersects the first opticalaxis plane. This leads to equal amounts of light of the first and secondoptical axes, thereby causing a problem that the illuminance of lightfor irradiating the document surface with light having a longer pathlength along the second optical axis differs from the illuminance oflight for irradiating the document surface with light along the firstoptical axis.

The present disclosure is made to solve the problems described above,and an objective of the present disclosure is to obtain a bidirectionallight emitting light guide that is compact and simple to assemble andhas a high illumination efficiency, a light source device using thelight guide, and an image reading device using the light guide.

Solution to Problem

To achieve the foregoing objective, according to a first aspect of thepresent disclosure, a light guide extending in a long axis direction andhaving an end in the long axis direction from which light enters thelight guide, includes a first exit portion for emitting first exitinglight, a second exit portion for emitting second exiting light in adirection different from a direction of the first exiting light, areflecting portion for reflecting light entering the light guide to eachof the first exit portion and the second exit portion.

The first exit portion has a first curved surface having a convex crosssection perpendicular to the long axis direction. The second exitportion has a second curved surface having a convex cross sectionperpendicular to the long axis direction. The second exit portion isconnected through a connection portion to the first exit portion to forma concave shape in the direction perpendicular to the long axisdirection.

The reflecting portion is disposed, in a plane portion facing both ofthe first exit portion and the second exit portion, at a position thatis shifted in the direction perpendicular to the long axis directionfrom a position where a normal to the plane passes through a connectionportion and intersects the plane portion, the connection portionconnecting the first exit portion and the second exit portion to form aconcave shape.

According to a second aspect of the present disclosure, an optical axisof the first exiting light and an optical axis of the second exitinglight intersect with each other.

According to a third aspect of the present disclosure, the first curvedsurface and the second curved surface have a same curvature.

According to a fourth aspect of the present disclosure, the first curvedsurface and the second curved surface form a continuous surface.

According to a fifth aspect of the present disclosure, the first curvedsurface and the second curved surface form a continuous surface, and thelight guide forms, in a cross section perpendicular to the long axisdirection, a shape obtained by connecting straight lines to the firstcurved surface and the second curved surface.

According to a sixth aspect of the present disclosure, the plane portionfacing the first exit portion and the plane portion facing the secondexit portion form, in a cross section perpendicular to the long axisdirection, a shape obtained by connecting straight lines.

According to a seventh aspect of the present disclosure, the planeportion facing the first exit portion and the plane portion facing thesecond exit portion have normals pointing in different directions.

According to an eighth aspect of the present disclosure, a second lightguide is retained in the housing, extending in the long axis directionand having an end in the long axis direction from which light enters thesecond light guide.

The second light guide comprises a third exit portion emitting thirdexiting light, and a third reflecting portion disposed in a planeportion facing the third exit portion, the second exiting light and thethird exiting light irradiate an area different from an area of theobject to be irradiated with the first exiting light, the imagingoptical system is disposed between the light guide and the second lightguide, and the housing retains the imaging optical system to focusscattered light, the scattered light being (i) the second exiting light,from the light guide, that is reflected on the object to be irradiatedand (ii) the third exiting light, from the second light guide, that isreflected on the object to be irradiated.

According to a ninth aspect of the present disclosure, an image readingdevice includes two light guide assemblies, a first unit and a secondunit, each including (i) a light guide extending in a long axisdirection and having an end in the long axis direction from which lightenters the light guide and (ii) a housing retaining the light guide, thefirst unit and the second unit being on opposing sides of an object tobe irradiated with the light from the light guide.

The light guide includes a first exit portion having a first curvedsurface having a convex cross section perpendicular to the long axisdirection, and emitting first exiting light, a second exit portionhaving a second curved surface having a convex cross sectionperpendicular to the long axis direction, being connected to the firstexit portion in a direction perpendicular to the long axis direction,and emitting second exiting light in a direction different from adirection of the first exiting light, a first reflecting portiondisposed in a plane portion facing the first exit portion, and a secondreflecting portion disposed in a plane portion facing the second exitportion.

The second exiting light irradiates an area different from an area ofthe object to be irradiated with the first exiting light.

The housing retains imaging optical system to focus scattered light, thescattered light being the second exiting light, from the light guide,that is reflected on the object to be irradiated.

The first exiting light emitted from the first unit enters the imagingoptical system of the second unit, and the first exiting light emittedfrom the second unit enters the imaging optical system of the firstunit.

According to a tenth aspect of the present disclosure, the plane portionfacing the first exit portion and the plane portion facing the secondexit portion have normals pointing in different directions, and theplane portion facing the first exit portion and the plane portion facingthe second exit portion form, in a cross section perpendicular to thelong axis direction, a shape obtained by connecting straight lines.

Advantageous Effects of Invention

According to the present disclosure, a bidirectional light emittinglight guide that is compact and simple to assemble and has a highillumination efficiency, a light source device using the light guide,and an image reading device using the light guide, can be obtained.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view of a light guide according to a firstembodiment of the present disclosure;

FIG. 2 is a top view as seen from a light diverting surface side of thelight guide according to the first embodiment;

FIG. 3 is a diagram illustrating an optical path in the longitudinalcross section of the light guide according to the first embodiment;

FIG. 4 is a diagram illustrating an optical path in the transverse crosssection of the light guide according to the first embodiment;

FIG. 5 is a diagram illustrating an optical path in the transverse crosssection of a light guide having a conventional configuration;

FIG. 6 is a cross-sectional view of a light guide according to a secondembodiment of the present disclosure;

FIG. 7 is a top view as seen from a light diverting surface side of thelight guide according to the second embodiment;

FIG. 8 is a diagram illustrating an optical path in the transverse crosssection of the light guide according to the second embodiment;

FIG. 9 is a cross-sectional view of a light guide according to a thirdembodiment of the present disclosure;

FIG. 10 is a diagram illustrating an optical path in the transversecross section of the light guide according to the third embodiment;

FIG. 11 is a cross-sectional view of a light guide according to a fourthembodiment of the present disclosure;

FIG. 12 is a diagram illustrating an optical path in the transversecross section of the light guide according to the fourth embodiment;

FIG. 13 is a cross-sectional view of a light guide according to a fifthembodiment of the present disclosure;

FIG. 14 is a diagram illustrating an optical path in the transversecross section of the light guide according to the fifth embodiment;

FIG. 15 is a cross-sectional view of a light guide according to a sixthembodiment of the present disclosure;

FIG. 16 is a diagram illustrating an optical path in the transversecross section of the light guide according to the sixth embodiment;

FIG. 17 is a cross-sectional view of a light guide according to aseventh embodiment of the present disclosure;

FIG. 18 is a diagram illustrating an optical path in the transversecross section of the light guide according to the seventh embodiment;

FIG. 19 is a diagram illustrating an optical path in the transversecross section of a light guide according to an eighth embodiment of thepresent disclosure;

FIG. 20 is a diagram illustrating an optical path in the transversecross section of a light guide without a notch, which is different fromthe light guide according to the eighth embodiment;

FIG. 21 is a diagram illustrating an optical path in the transversecross section of a light guide without a notch, which is different fromthe light guide according to the eighth embodiment;

FIG. 22 is a diagram illustrating an optical path in the transversecross section of a light guide with two notches according to the eighthembodiment;

FIG. 23 is a diagram illustrating an optical path in the transversecross section of a light guide with notches according to the eighthembodiment, with the cutting direction adjusted;

FIG. 24 is a diagram illustrating an optical path in the transversecross section of a light guide with notches according to the eighthembodiment, with the cutting plane angle thereof adjusted;

FIG. 25 is a diagram illustrating an optical path in the transversecross section of a light guide with notches according to the eighthembodiment, the notches each being provided with a light blockingmember;

FIG. 26 is an exploded view illustrating the structure of a light sourcedevice according to a ninth embodiment of the present disclosure;

FIG. 27 is an exploded view illustrating a light source part of thelight source device according to the ninth embodiment;

FIG. 28 is a top view of the light source device according to the ninthembodiment;

FIG. 29A is an enlarged cross-sectional view of the vicinity of thelongitudinal end of the light source device according to the ninthembodiment;

FIG. 29B is a longitudinal sectional view of the light source deviceaccording to the ninth embodiment;

FIG. 30A is a development view of a plate-like member constituting ahousing according to the ninth embodiment;

FIG. 30B is a development view of a plate-like member constituting alight guide holder according to the ninth embodiment;

FIG. 30C is a development view of a plate-like member constituting amirror mounting surface according to the ninth embodiment;

FIG. 31A is a diagram illustrating an optical path in the longitudinalcross section of the entire light source device according to the ninthembodiment;

FIG. 31B is a diagram illustrating an optical path in the longitudinalcross section of the vicinity of the end of the light source deviceaccording to the ninth embodiment;

FIG. 32 is a diagram illustrating an optical path in the transversecross section of the light source device according to the ninthembodiment;

FIG. 33 is a view of a cross section perpendicular to a main scanningdirection, of an image reading device using an image sensor according toa tenth embodiment of the present disclosure;

FIG. 34 is an exploded view of the image reading device according to thetenth embodiment;

FIG. 35 is an external view with a glass side up of the image readingdevice according to the tenth embodiment;

FIG. 36 is an external view with a signal processing board side up ofthe image reading device according to the tenth embodiment; and

FIG. 37 is a view of a cross section perpendicular to a main scanningdirection, of an image reading device using an image sensor according toan eleventh embodiment of the present disclosure.

DESCRIPTION OF EMBODIMENTS First Embodiment

The structure and operation of a light guide according to a firstembodiment of the present disclosure are described with reference toFIGS. 1 to 4.

FIG. 1 is a cross-sectional view of the light guide according to thefirst embodiment of the present disclosure. FIG. 2 is a top view as seenfrom a light diverting surface side of the light guide according to thefirst embodiment of the present disclosure. FIG. 3 is a diagramillustrating an optical path (path of light) in the longitudinal(hereinafter also referred to as “long axis direction”) cross section ofthe light guide according to the first embodiment of the presentdisclosure. FIG. 4 is a diagram illustrating an optical path in thetransverse cross section of the light guide according to the firstembodiment of the present disclosure. As used herein, “transverse”direction refers to any one of the directions perpendicular to the longaxis direction (longitudinal direction), and so forth.

The light guide 1 according to the present embodiment extends in thelong axis direction, and incident light enters the light guide 1 from anentry portion disposed at the long axis direction end thereof. The lightguide 1 includes a light diverting surface (reflecting portion) 1 a forreflecting light entering the light guide 1, an exit portion (first exitportion) 1 b for emitting primary light (first exiting light) 1 h, andan exit portion (second exit portion) 1 c for emitting secondary light(second exiting light) 1 i in a direction different from the directionof the primary light (first exiting light) 1 h.

The exit portion 1 b has a first curved surface (first exit surface)having a convex cross section perpendicular to the long axis direction.The exit portion 1 c continues (connects) to the exit portion 1 b in thedirection perpendicular to the long axis direction and has a secondcurved surface (second exit surface) having a convex cross sectionperpendicular to the long axis direction.

The light diverting surface 1 a is disposed at the point of intersectionbetween optical axes of primary light 1 h and secondary light 1 i. Thelight diverting surface 1 a reflects light entering the light guide 1 toeach of the exit portions 1 b and 1 c. This light diverting surface 1 adiverts (splits) light entering the light guide 1 into primary light 1 hand secondary light 1 i.

The exit portions 1 b and 1 c are connected at a linear commonconnection portion (connection portion) extending in the longitudinaldirection. The exit portions 1 b and 1 c connected at the commonconnection portion to form a concave shape therebetween in thetransverse cross section.

The light diverting surface 1 a is disposed in a plane facing the exitportions 1 b and 1 c. The light diverting surface 1 a is displaced(shifted) from a line vertical to the plane and passing through thecommon connection portion to the exit portion (first exit portion) 1 bin the direction perpendicular to the long axis direction. Morespecifically, the light diverting surface 1 a is disposed, in the planefacing the first exit portion 1 b and the second exit portion 1 c, at aposition that is shifted in the direction perpendicular to the long axisdirection from a position where the normal to the plane passes throughthe common connection portion between the first exit portion 1 b and thesecond exit portion 1 c.

The light guide 1 is a rod-shaped member formed of a transparent resinand extending in the longitudinal direction. The profile of the lightguide 1 according to the present embodiment, in the cross sectionperpendicular to the longitudinal direction, is composed of threestraight lines and two curved lines (see FIG. 1).

Specifically, the light guide 1 according to the present embodiment has,along the entire longitudinal extent, the light diverting surface 1 a,the exit portions 1 b and 1 c having curved surfaces, a bottom surfaceprovided with the light diverting surface 1 a, a side surface 1 dconnecting the bottom surface and the exit portion 1 b, and a sidesurface 1 e connecting the bottom surface and the curved exit portion 1c.

The light diverting surface 1 a has a white printed pattern or unevenshape formed along the longitudinal direction of the light guide 1. Whena normal is drawn from a longitudinally-extending linear recess (commonconnection portion), which forms a boundary line between the exitportions 1 b and 1 c, to the bottom surface provided with the lightdiverting surface 1 a, the light diverting surface 1 a is located at theexit portion 1 b side with respect to the normal and is displaced(shifted) so that the light diverting surface 1 a does not exist at theexit portion 1 c side.

As illustrated in FIG. 3, light entering the light guide 1 from an entrysurface 1 g disposed at the longitudinal end thereof travelslongitudinally while being reflected on the wall surface of the lightguide 1 repeatedly. A portion of longitudinally traveling light isincident on the light diverting surface 1 a. The portion of lightincident on the light diverting surface 1 a is reflected and thusemitted from the exit portion 1 b facing the light diverting surface 1 aas linear primary light 1 h extending in the longitudinal direction. Theportion of light incident on the light diverting surface 1 a exits fromthe exit portion 1 c as linear secondary light 1 i extending in thelongitudinal direction. In this way, a single light guide emits light intwo directions. Light not incident on the light diverting surface 1 a isguided within the light guide 1 longitudinally and exits from the otherentry surface 1 g at the end opposite to the entry surface 1 g.

As illustrated in FIG. 4, light reflected by the light diverting surface1 a is incident on the exit portions 1 b and 1 c and is focused at anorientation angle by the curved surfaces of the exit portions 1 b and 1c. As described above, the light diverting surface 1 a has a whiteprinted pattern or uneven shape formed along the longitudinal directionof the light guide 1. In addition, when a normal is drawn from alongitudinally-extending linear recess, which forms a boundary linebetween the exit portions 1 b and 1 c, to the bottom surface, the lightdiverting surface 1 a is located at the exit portion 1 b side of thebottom surface with respect to the normal and does not exist at the exitportion 1 c side. Therefore, the light intensity of primary light 1 h issufficiently higher than the light intensity of secondary light 1 i. Theorientation angles of primary light 1 h and secondary light 1 i can becontrolled at an angle according to the respective shapes of the exitportions 1 b and 1 c. The bottom surface 1 k of the light guide 1 exceptfor the light diverting surface 1 a serves as a light guiding surfacefor guiding light therein longitudinally by reflection, similarly to theother surfaces of the light guide 1. The bottom surface 1 k and the sidesurfaces 1 d and 1 e of the light guide 1 are planar, which enables easymechanical assembly.

A conventional example is described hereinafter to illustrate theeffects of the light guide 1 according to the first embodiment of thepresent disclosure.

FIG. 5 illustrates an optical path in the transverse cross section of alight guide having a conventional configuration. In this drawing, thelight diverting surface 1 a is provided across the entire bottomsurface. Thus when a normal is drawn from a linear recess, which forms aboundary line between the exit portions 1 b and 1 c, to the bottomsurface, unintended light emission is caused by reflection on the lightdiverting portion 1 a except for a portion positioned at the exitportion 1 b side with respect to the normal, that is, by reflection onthe light diverting portion 1 a in a portion positioned at the exitportion 1 c side with respect to the normal and a portion correspondingto the boundary line between the exit portions 1 b and 1 c are providedwith the light diverting surface 1 a. A problem of increased secondarylight 1 i thereby arises.

In addition, the light diverting surface 1 a is wide in the transversedirection, thus causing exiting light to contain light in variousdirections. This results in a problem of a wider orientation angles.Furthermore, light from the light diverting surface 1 a that ispositioned on the normal drawn from the boundary line between the exitportions 1 b and 1 c to the bottom surface becomes stray light exitingfrom the boundary line between the exit portions 1 b and 1 c, whichcauses difficulties in obtaining light in two intended directions only.

The light guide 1 according to the present embodiment can eliminate orreduce unintended light emission. As a result, light split into twointended directions can be obtained.

Second Embodiment

The structure and operation of a light guide according to a secondembodiment of the present disclosure are described with reference toFIGS. 6 to 8.

FIG. 6 is a cross-sectional view of the light guide according to thesecond embodiment of the present disclosure. FIG. 7 is a top view asseen from a light diverting surface side of the light guide according tothe second embodiment of the present disclosure. FIG. 8 is a diagramillustrating an optical path in the transverse cross section of thelight guide according to the second embodiment of the presentdisclosure. In FIGS. 6 to 8, same reference signs denote the same orsimilar components to those in FIGS. 1 to 4, and further descriptionsthereof are omitted here.

The light guide 1 according to the present embodiment includes a lightdiverting surface 1L in addition to the configuration of the light guide1 according to the first embodiment. A light diverting surface 1 a as afirst reflecting portion is provided on a bottom surface (plane) 1 kfacing an exit portion (first exit portion) 1 b. A light divertingsurface 1L as a second reflecting portion is provided on a bottomsurface (plane) 1 m facing an exit portion (second exit portion) 1 c.The distance between the exit portion 1 b and the light divertingsurface 1 a is shorter than the distance between the exit portion 1 cand the light diverting surface 1L. The exit portions 1 b and 1 c areconnected at a common connection portion to form a concave shape in thecross section perpendicular to the longitudinal direction of the lightguide 1 (see FIG. 6). The light diverting surfaces 1 a and 1L arearranged in parallel in a direction perpendicular to the longitudinaldirection of the light guide 1 (see FIG. 7).

The light guide 1 is a rod-shaped member formed of a transparent resinand extending in the longitudinal direction. The profile of the lightguide 1 according to the present embodiment, in the cross sectionperpendicular to the longitudinal direction, is composed of fivestraight lines and two curved lines (see FIG. 6).

Specifically, the light guide 1 according to the present embodiment has,along the entire longitudinal extent, the light diverting surface 1 a,the exit portions 1 b and 1 c having curved surfaces, a bottom surface 1k provided with the light diverting surface 1 a, a side surface 1 dconnecting the bottom surface 1 k and the exit portion 1 b, a bottomsurface 1 m provided with the light diverting surface 1L, a side surface1 e connecting the bottom surface 1 m and the exit portion 1 c, and aside surface connecting the bottom surfaces 1 k and 1 m.

The light diverting surface 1 a has a white printed pattern or unevenshape formed along the longitudinal direction of the light guide 1 andfaces the exit portion 1 b. The light diverting surface 1L has a whiteprinted pattern or uneven shape formed along the longitudinal directionof the light guide 1 and faces the exit portion 1 c, and the bottomsurfaces 1 k and 1 m are parallel to each other. The distance betweenthe exit portion 1 b and the light diverting surface 1 a is shorter thanthe distance between the exit portion 1 c and the light divertingsurface 1L. The light diverting surfaces 1 a and 1L are arranged inparallel in a direction perpendicular to the longitudinal direction ofthe light guide 1 (see FIG. 7).

As illustrated in FIG. 8, light reflected by the light diverting surface1L is incident on the exit portions 1 b and 1 c and is focused at anorientation angle by the curved surfaces of the exit portions 1 b and 1c. Light reflected by the light diverting surface 1 a is incident on theexit portion 1 b and is focused at an orientation angle by the curvedsurface of the exit portion 1 b. That is, since the distance between theexit portion 1 b and the light diverting surface 1 a is shorter than thedistance between the exit portion 1 c and the light diverting surface1L, light reflected by the light diverting surface 1L is incident on theexit portions 1 b and 1 c, but light reflected by the light divertingsurface 1 a is not incident on the exit portion 1 c.

Therefore, the light intensity of primary light 1 h is sufficientlyhigher than the light intensity of secondary light 1 i. The lightdiverting surfaces 1 a and 1L each have a white printed pattern oruneven shape formed along the longitudinal direction of the light guide1. The orientation angles of primary light 1 h and secondary light 1 ican be controlled at an angle according to the respective shapes of theexit portions 1 b and 1 c. The bottom surfaces 1 k and 1 m of the lightguide 1, except for the light diverting surfaces 1 a and 1L, serve aslight guiding surfaces similarly to the other surfaces of the lightguide 1. The bottom surfaces and the side surfaces 1 d and 1 e of thelight guide 1 are planar, which enables easy mechanical assembly.

The light guide 1 according to the present embodiment enables the singlelight guide 1 to emit light in two directions.

Third Embodiment

The structure and operation of a light guide according to a thirdembodiment of the present disclosure are described with reference toFIGS. 9 and 10.

FIG. 9 is a cross-sectional view of a light guide according to a thirdembodiment of the present disclosure. FIG. 10 is a diagram illustratingan optical path in the transverse cross section of the light guideaccording to the third embodiment of the present disclosure. In FIGS. 9and 10, same reference signs denote the same or similar components tothose in FIGS. 6 to 8, and further descriptions thereof are omittedhere.

The light guide 1 is a rod-shaped member formed of a transparent resinand extending in the longitudinal direction. The light guide 1 accordingto the present embodiment has a profile in a cross section perpendicularto the longitudinal direction, or a transverse profile, composed of fivestraight lines and two curved lines (see FIG. 9).

Specifically, the light guide 1 according to the present embodiment hasa bottom surface 1 k having a light diverting surface 1 a extendingalong the entire longitudinal extent and a bottom surface 1 m having alight diverting surface 1L extending along the entire longitudinalextent. The bottom surface 1 m is positioned outside a round-shapedlight guide. The bottom surfaces 1 k and 1 m connect smoothly through aside surface 1 d. An exit portion 1 b and the bottom surface 1 m connectsmoothly through a side surface 1 e. That is, the light divertingsurfaces 1 a and 1L have respective normals pointing in differentdirections (see FIG. 9). The cross section perpendicular to thelongitudinal direction of the light guide 1 has a convex shapeprojecting outward from a round shape by the side surfaces 1 d and 1 eand the bottom surface 1 m.

The light diverting surface 1 a has a white printed pattern or unevenshape formed along the longitudinal direction of the light guide 1 andis positioned at the outer periphery of the round part in the crosssection perpendicular to the longitudinal direction. A first curvedsurface of the exit portion 1 b and a second curved surface of the exitportion 1 c have the same curvature, and the exit portions 1 b and 1 cform a smooth continuous curved surface. The distance between the exitportion 1 b and the light diverting surface 1 a is shorter than thedistance between the exit portion 1 c and the light diverting surface1L.

As illustrated in FIG. 10, light reflected by the light divertingsurface 1 a is focused at an orientation angle by the exit portion 1 b,whereas light reflected by the light diverting surface 1L is focused atan orientation angle by the exit portion 1 c. The optical axis ofprimary light 1 h exiting from the exit portion 1 b intersects theoptical axis of secondary light 1 i emitted from the exit portion 1 c.

As described above, the light diverting surface 1L is positioned, in thecross section perpendicular to the longitudinal direction, at the tip ofa convex shaped portion formed from a part of the circular shape of thelight guide 1, and has a white printed pattern or uneven shape formedalong the longitudinal direction.

The bottom surface 1 m projects sufficiently from the circular-shapedportion in the cross section perpendicular to the longitudinaldirection. Thus the direction of light can be controlled due to thereflection on the side surfaces 1 d and 1 e.

The light guide 1 according to the present embodiment enables the singlelight guide to emit light in two directions.

In addition, the distance from the light diverting surface 1 a to theexit portion 1 b is shorter than the distance from the light divertingsurface 1L to the exit portion 1 c. Therefore, the amount of primarylight 1 h emitted from the exit portion 1 b is greater than the amountof secondary light 1 i emitted from the exit portion 1 c.

Fourth Embodiment

The structure and operation of a light guide according to a fourthembodiment of the present disclosure are described with reference toFIGS. 11 and 12. FIG. 11 is a cross-sectional view of the light guideaccording to the fourth embodiment of the present disclosure. FIG. 12 isa diagram illustrating an optical path in the transverse cross sectionof the light guide according to the fourth embodiment of the presentdisclosure. In FIGS. 11 and 12, same reference signs denote the same orsimilar components to those in FIGS. 9 and 10, and further descriptionsthereof are omitted here.

The light guide 1 according to the present embodiment is formed of atransparent resin and extends in the longitudinal direction. The lightguide 1 according to the present embodiment forms a shape, in thetransverse cross section, of two circles (round parts) 110 and 111connected so that the circles have a common chord. The light guide 1according to the present embodiment has a bottom surface 1 k having alight diverting surface 1 a extending along the entire longitudinalextent and a bottom surface 1 m having a light diverting surface 1Lextending along the entire longitudinal extent. In the transverse crosssection, the bottom surface 1 m is positioned outside a round-shapedlight guide. The bottom surfaces 1 k and 1 m connect through a curvedside surface 1 d. An exit portion 1 b and the bottom surface 1 m connectthrough a curved side surface 1 e.

The light guide 1 according to the present embodiment is a rod-shapedmember extending in the longitudinal direction and having a circularcross section perpendicular to the longitudinal direction. The lightdiverting surface 1 a has a white printed pattern or uneven shape formedalong the longitudinal direction of the light guide 1. The lightdiverting surface 1 a is positioned at the outer periphery of the roundpart 110 in the transverse cross section. Exit portions 1 b and 1 c areformed in different portions of the round part 110 in the transversecross section and form a smooth continuous curved surface. In addition,the normal to the bottom surface 1 m is on a line extending throughcenters of two circles 110 and 111. The distance between the exitportion 1 b and the light diverting surface 1 a is shorter than thedistance between the exit portion 1 c and the light diverting surface1L.

As illustrated in FIG. 12, light reflected by the light divertingsurface 1 a is focused at an orientation angle by the exit portion 1 b,whereas light reflected by the light diverting surface 1L is focused atan orientation angle by the exit portion 1 c. The optical axis ofprimary light 1 h emitted from the exit portion 1 b intersects theoptical axis of secondary light 1 i emitted from the exit portion 1 c.

As described above, the light diverting surface 1L is positioned, in thecross section perpendicular to the longitudinal direction, at the tip ofa convex shaped portion formed from a part of the circle 110 of thelight guide 1, and has a white printed pattern or uneven shape formedalong the longitudinal direction.

The bottom surface 1 m projects sufficiently from the circle 110 in thecross section perpendicular to the longitudinal direction. Thus thedirection of light can be controlled due to the shielding effect of theportions connecting two circles 110 and 111.

The light guide 1 according to the present embodiment enables the singlelight guide to emit light in two directions.

In addition, the distance from the light diverting surface 1 a to theexit portion 1 b is shorter than the distance from the light divertingsurface 1L to the exit portion 1 c. Therefore, the amount of primarylight 1 h emitted from the exit portion 1 b is greater than the amountof secondary light 1 i emitted from the exit portion 1 c.

Fifth Embodiment

The structure and operation of a light guide according to a fifthembodiment of the present disclosure are described with reference toFIGS. 13 and 14. FIG. 13 is a cross-sectional view of the light guideaccording to the fifth embodiment of the present disclosure. FIG. 14 isa diagram illustrating an optical path in the transverse cross sectionof the light guide according to the fifth embodiment of the presentdisclosure. In FIGS. 13 and 14, same reference signs denote the same orsimilar components to those in FIGS. 9 and 10, and further descriptionsthereof are omitted here.

The light guide 1 is a rod-shaped member formed of a transparent resinand extending in the longitudinal direction. The light guide 1 accordingto the present embodiment forms a shape obtained by connecting threesides of a rectangle to a circle in the transverse cross section (seeFIG. 13).

The light guide 1 according to the present embodiment has a bottomsurface 1 m having a light diverting surface 1L extending along theentire longitudinal extent and a planar surface 1 k having a lightdiverting surface 1 a extending along the entire longitudinal extent.The planar surface 1 k connects smoothly to an exit portion 1 c. In thetransverse cross section, the bottom surface 1 m is positioned outsidethe round-shaped portion. One side surface (side wall portion) 1 d isplanar. An end of the one side surface (side wall portion) 1 d isperpendicular to an end (left end in FIG. 13) of the bottom surface(plane facing a second exit portion 1 c) 1 m in the transverse crosssection. The other end of the one side surface (side wall portion) 1 dextends to connect to a first curved surface of a first exit portion 1 b(to connect smoothly to the exit portion 1 b) in the transverse crosssection. An end of the other side surface 1 e is perpendicular to theother end (right end in FIG. 13) of the bottom surface 1 m and the otherend of the other side surface 1 e connects to an end (lower end in FIG.13) of the planar surface 1 k in the transverse cross section. Inaddition, the planar surface 1 k and the bottom surface 1 m haverespective normals pointing in different directions.

The light diverting surface 1 a has a white printed pattern or unevenshape formed along the longitudinal direction of the light guide 1 andis positioned at the outer periphery of a round part in the transversecross section. The first and second curved surfaces have the samecurvature, and the exit portions 1 b and 1 c form a smooth continuouscurved surface. The distance between the exit portion 1 b and the lightdiverting surface 1 a is shorter than the distance between the exitportion 1 c and the light diverting surface 1L.

As illustrated in FIG. 14, light reflected by the light divertingsurface 1 a is focused at an orientation angle by the exit portion 1 b,whereas light reflected by the light diverting surface 1L is focused atan orientation angle by the exit portion 1 c. In addition, the sidesurface 1 d reflects light reflected by the reflecting portion 1L to theexit portion 1 c and guides light in the long axis direction of thelight guide 1. The bottom surface 1 m projects sufficiently from thecircle in the cross section perpendicular to the longitudinal direction.Thus the direction of light can be controlled due to the reflection onthe side surfaces 1 d and 1 e.

The light guide 1 according to the present embodiment enables the singlelight guide to emit light in two directions.

In addition, the distance from the light diverting surface 1 a to theexit portion 1 b is shorter than the distance from the light divertingsurface 1L to the exit portion 1 c. Therefore, the amount of primarylight 1 h emitted from the exit portion 1 b is greater than the amountof secondary light 1 i emitted from the exit portion 1 c.

Sixth Embodiment

The structure and operation of a light guide according to a sixthembodiment of the present disclosure are described with reference toFIGS. 15 and 16.

FIG. 15 is a cross-sectional view of the light guide according to thesixth embodiment of the present disclosure. FIG. 16 is a diagramillustrating an optical path in the transverse cross section of thelight guide according to the sixth embodiment of the present disclosure.In FIGS. 15 and 16, same reference signs denote the same or similarcomponents to those in FIGS. 9 and 10, and further descriptions thereofare omitted here.

The light guide 1 is a rod-shaped member formed of a transparent resinand extending in the longitudinal direction. In a cross sectionperpendicular to the longitudinal direction, the light guide 1 accordingto the present embodiment forms a shape obtained by connecting anellipse to a circle (see FIG. 15).

The light guide 1 according to the present embodiment has a bottomsurface 1 m having a light diverting surface 1L extending along theentire longitudinal extent and a planar surface 1 k having a lightdiverting surface 1 a extending along the entire longitudinal extent.The planar surface 1 k connects smoothly to the exit portion 1 c. In thecross section perpendicular to the longitudinal direction, the bottomsurface 1 m is positioned outside a round-shaped light guide. One sidesurface 1 d of the bottom surface 1 m is a curved surface and has aconvex shape in the transverse cross section. In the transverse crosssection, an end of the one side surface (side wall portion) 1 d connectsto an end (left end in FIG. 15) of a plane facing a second exit portion1 c. In the transverse cross section, the other end of the one sidesurface (side wall portion) 1 d extends to connect to a first curvedsurface of a first exit portion 1 b. The other side surface 1 e of thebottom surface 1 m connects to the planar surface 1 k.

The side surfaces 1 d and 1 e each have an identical focal point on thelight diverting surface 1L, so that light scattered by the lightdiverting surface 1L is reflected as collimated light. In addition, theplanar surface 1 k and the bottom surface 1 m have respective normalspointing in different directions.

The light diverting surface 1 a has a white printed pattern or unevenshape formed along the longitudinal direction of the light guide 1 andis positioned at the outer periphery of the round part in the crosssection perpendicular to the longitudinal direction. The exit portion 1b has a smooth curved surface (first curved surface) and is continuouswith the planar exit portion 1 c. In the present embodiment, the exitportion 1 c is a plane, but may be a curved surface.

As illustrated in FIG. 16, light reflected by the light divertingsurface 1 a is focused at an orientation angle by the exit portion 1 b,whereas light reflected by the light diverting surface 1L is focused atan orientation angle by the exit portion 1 c. In addition, the sidesurface 1 d reflects light reflected by the reflecting portion 1L to theexit portion 1 c and guides light in the long axis direction of thelight guide 1. The bottom surface 1 m projects sufficiently from thecircle in the cross section perpendicular to the longitudinal direction.Thus the direction of light can be controlled due to the reflection onthe side surfaces 1 d and 1 e.

The light guide 1 according to the present embodiment enables the singlelight guide 1 to emit light in two directions.

Seventh Embodiment

The structure and operation of a light guide according to a seventhembodiment of the present disclosure are described with reference toFIGS. 17 and 18.

FIG. 17 is a cross-sectional view of the light guide according to theseventh embodiment of the present disclosure. FIG. 18 is a diagramillustrating an optical path in the transverse cross section of thelight guide according to the seventh embodiment of the presentdisclosure. In FIGS. 17 and 18, same reference signs denote the same orsimilar components to those in FIGS. 9 and 10, and further descriptionsthereof are omitted here.

The light guide 1 is a rod-shaped member formed of a transparent resinand extending in the longitudinal direction. In a cross sectionperpendicular to the longitudinal direction, the light guide 1 accordingto the present embodiment forms a shape obtained by connecting fourstraight lines to a circle.

The light guide 1 according to the present embodiment has a bottomsurface 1 k having a light diverting surface 1 a extending along theentire longitudinal extent and a bottom surface 1 m having a lightdiverting surface 1L extending along the entire longitudinal extent. Oneside surface 1 f connects smoothly to an exit portion 1 c. The otherside surface 1 f connects smoothly to an exit portion 1 b. The one sidesurface 1 f and the other side surface 1 f connect via the bottomsurfaces 1 k and 1 m. In addition, the planar surface 1 m and the bottomsurface 1 k have respective normals pointing in different directions.The exit portions 1 b and 1 c form a smooth continuous curved surface.The light diverting surface 1 a has an area larger than the area of thelight diverting surface 1L. That is, the light diverting surface 1 a hasa transverse length longer than the length of the light divertingsurface 1L.

As illustrated in FIG. 18, light reflected by the light divertingsurface 1 a is focused at an orientation angle by the exit portion 1 b,whereas light reflected by the light diverting surface 1L is focused atan orientation angle by the exit portion 1 c.

The light guide 1 according to the present embodiment enables the singlelight guide to emit light in two directions.

The light diverting surface 1 a has an area larger than the area of thelight diverting surface 1L, so that the amount of primary light 1 hemitted from the exit portion 1 b is greater than the amount ofsecondary light 1 i emitted from the exit portion 1 c.

Eighth Embodiment

The structure and operation of a light guide according to an eighthembodiment of the present disclosure are described with reference toFIGS. 19 to 25.

FIG. 19 is a diagram illustrating an optical path in the transversecross section of the light guide according to the eighth embodiment ofthe present disclosure. In FIGS. 19 to 25, same reference signs denotethe same or similar components to those in FIGS. 9 and 10, and furtherdescriptions thereof are omitted here.

The light guide 1 is a rod-shaped member formed of a transparent resinand extending in the longitudinal direction. The light guide 1 accordingto the present embodiment forms a circular shape in a cross sectionperpendicular to the longitudinal direction.

A side surface 1 f between a first exit portion 1 b and a lightdiverting surface 1L is provided with a notch (recess) 1 p along theentire longitudinal extent. The notch 1 p is formed of planar sidesurfaces 1 f and 1 r. The side surfaces 1 f and 1 r are perpendicular toeach other in the transverse cross section. The side surface 1 f of thenotch 1 p is parallel to the optical axis of primary light 1 h in thetransverse cross section.

The light guide 1 according to the present embodiment has a bottomsurface 1 k having a light diverting surface 1 a extending along theentire longitudinal extent and a bottom surface 1 m having a lightdiverting surface 1L extending along the entire longitudinal extent.Exit portions 1 c and 1 b form a smooth continuous curved surface andare connected smoothly in the transverse cross section. The other sidesurface 1 f of the notch 1 p connects smoothly to the exit portion 1 bin the transverse cross section. The one side surface 1 f and the otherside surface 1 r are perpendicular to each other in the transverse crosssection, as described above. The other side surface 1 r connects to theexit portion 1 c via bottom surfaces 1 k and 1 m, a curved surface 1 ethat is smoothly continuous with the exit portion 1 c, and the like inthe transverse cross section. In addition, the planar surface 1 m andthe bottom surface 1 k have respective normals pointing in differentdirections.

A light guide 1 illustrated in FIG. 20 is different from the light guide1 illustrated in FIG. 19 in that the side surface has no notches, andthe light diverting surface 1L scatters more. In this case, secondarylight 1 i extends wider, thus overlapping with primary light 1 h. Lightirradiation of an object to be irradiated (object to be read) in thisoverlapped state causes the secondary light 1 i to have a greaterincident angle with respect to the object to be irradiated. This resultsin shifts in illumination position and large changes in brightness whenthe distance between a glass on which the object to be irradiated ismounted and the object to be irradiated varies depending on positioning.Accordingly, providing the notch 1 p on the side surface of the lightguide 1, as illustrated in FIG. 19, blocks an optical path that maycause wider secondary light 1 i.

FIG. 21 illustrates a light guide 1 with light diverting surfaces 1 aand 1L having larger scattering angles. As illustrated in FIG. 22, thislight guide 1 also eliminates or reduces overlapping of primary light 1h and secondary light 1 i by providing notches 1 p and 1 q in the sidesurfaces. Here, the notch 1 p is formed by planar surfaces 1 f and 1 r.The side surfaces 1 f and 1 r are perpendicular to each other. The notch1 q is formed of planar side surfaces 1 e and 1 n. The side surfaces 1 eand 1 n are perpendicular to each other. In addition, the side surface 1f is parallel to the optical axis of primary light 1 h. The side surface1 e is parallel to the optical axis of secondary light 1 i.

The light guide 1 as illustrated in FIG. 22 is provided with the notches1 p and 1 q such that the side surface 1 f of the notch 1 p is parallelto the optical axis of primary light 1 h and the side surface 1 e of thenotch 1 q is parallel to the optical axis of secondary light 1 i. Inthis case, a mold is required to be opened in a direction perpendicularto an average angle of light exit angles of primary light 1 h andsecondary light 1 i, thus forming the joint of the mold between the exitportions 1 c and 1 b. The joint line of the mold between the exitportions 1 c and 1 b may cause refraction of exiting light. Thus, alight guide 1 as illustrated in FIG. 23 as another modified example isprovided with notches 1 p and 1 q such that a side surface 1 f of thenotch 1 p is parallel to the optical axis of primary light 1 h and aside surface 1 n of the notch 1 q is parallel to the optical axis ofprimary light 1 h. This prevents the joint line from being formedbetween the exit portions 1 c and 1 b, because the mold opens in thedirection of primary light 1 h.

Only the notches of the light guide 1 as illustrated in FIG. 23 causesan optical path 1 h′ of light that reenters the light guide from thenotch 1 q after exiting from the side surface of the notch 1 q. Primarylight 1 h may be spread widely thereby. Accordingly, as another modifiedexample, inclined side surfaces of the notches 1 p and 1 q may beformed, as illustrated in the light guide 1 in FIG. 24, to preventprimary light 1 h from extending wider by this optical path. That is,the side surfaces 1 e and 1 n and the side surfaces 1 f and 1 r areformed so that the intersection angles between the side surfaces 1 e and1 n and between the side surfaces 1 f and 1 r are obtuse angles.

In addition, as in a light guide 1 illustrated in FIG. 25, light may beblocked by providing light blocking members 30 sized so as to fit intothe notches 1 p and 1 q. The light blocking member 30 may be made ofhigh reflective material such as metal and white resin. This enableslight leaking from the light guide 1 to reenter the light guide 1, thusincreasing illumination light amount.

Ninth Embodiment

A light source device according to a ninth embodiment of the presentdisclosure is described with reference to the drawings. In the presentembodiment, a bifurcated linear light source device using a light guide1 according to the first embodiment is described.

FIG. 26 is an exploded view illustrating the structure of the bifurcatedlinear light source device according to the ninth embodiment of thepresent disclosure. FIG. 27 is an exploded view illustrating a lightsource part of the bifurcated linear light source device according tothe ninth embodiment of the present disclosure. FIG. 28 is a top view ofthe bifurcated linear light source device according to the ninthembodiment of the present disclosure. FIG. 29A is a cross-sectional viewof the vicinity of the longitudinal end of the bifurcated linear lightsource device according to the ninth embodiment of the presentdisclosure. FIG. 29B is a longitudinal sectional view of the bifurcatedlinear light source device according to the ninth embodiment of thepresent disclosure. FIG. 30A is a development view of a plate-likemember constituting a housing according to the ninth embodiment of thepresent disclosure. FIG. 30B is a development view of a plate-likemember constituting a light guide holder according to the ninthembodiment of the present disclosure. FIG. 30C is a development view ofa plate-like member constituting a mirror mounting surface according tothe ninth embodiment of the present disclosure. FIG. 31A is a diagramillustrating an optical path in the longitudinal cross section of thebifurcated linear light source device according to the ninth embodimentof the present disclosure. FIG. 31B is a diagram illustrating an opticalpath in the longitudinal cross section of the vicinity of the end of thebifurcated linear light source device, or the vicinity of a lightemitter, according to the ninth embodiment of the present disclosure.FIG. 32 is a diagram illustrating an optical path in the transversecross section of the bifurcated linear light source device according tothe ninth embodiment of the present disclosure.

The structure and operation of the bifurcated linear light source deviceaccording to the ninth embodiment are described with reference to FIGS.26 to 32. The light guide 1 is, as described in the first embodiment, arod-shaped member formed of a transparent resin and extending in thelongitudinal direction, and has a light diverting surface 1 a along theentire longitudinal extent and curved exit portions 1 b and 1 c.

A mirror (reflector) 12 is arranged in parallel to the light guide 1 inthe longitudinal direction, reflects primary light 1 h emitted from thelight guide 1, and emits the reflected secondary light in the directionof a document mount. The mirror 12 is constructed of, for example, ametallized surface, and has a thin plate-like or sheet-like formextending in the longitudinal direction. The mirror 12 is fixed on themirror mounting surface 6 g of a housing 6, by adhesion or the like, andis maintained at appropriate distance and angle with respect to thelight guide 1 and the document mount.

A light emitter 2 is a light source element such as a light emittingdiode (LED) light source and is fixed on a light emitter mounting board4 by soldering or the like. The light emitter 2 is driven with currentby the light emitter mounting board 4 to emit light. The light emitter 2emits light and the light enters the light guide 1 from one longitudinalend surface thereof.

A light emitter 3 is a light source element such as an LED light sourceand is fixed on a light emitter mounting board 5 by soldering or thelike. The light emitter 3 is driven with current by the light emittermounting board 5 to emit light. The light emitter 3 emits light and thelight enters the light guide 1 from an end surface thereof at theopposite side to the light emitter 2 side of the light guide 1.

An optical filter 10 is a member that uses glass or polyethyleneterephthalate (PET) resin sheet as a base material so as to alteroptical properties. The optical filter 10 is a filter that obtainsexcitation light using, for example, phosphors or the like, or aband-pass filter or the like that removes unnecessary wavelengths. Theoptical filter 10 is fixed on a holder 8 by adhesion or the like. Theoptical filter 10 may be disposed between the light emitter 2 and thelight guide 1 so as to face the light emitter 2, and the optical filter10 may be disposed between the light emitter 3 and the light guide 1 soas to face the light emitter 3.

The holder 8 retains the light emitter mounting board 4, the opticalfilter 10, and a fin 9 and eliminates or reduces unintended light fromthe light emitters 2 and 3 and the light guide 1. An end portionincluding one end surface of a light guide holder 7 may be inserted intoone longitudinal end surface of the holder 8. At the opposite side ofthe end surface of the holder 8 in the longitudinal direction, the lightemitter mounting board 4 and the light emitter 2 may be disposed so asto face the light guide 1. In addition, an end portion including one endsurface of the light guide holder 7 is inserted into the onelongitudinal end surface of the holder 8, and at the opposite side ofthe end surface of the holder 8 in the longitudinal direction, the lightemitter mounting board 5 and the light emitter 3 may be disposed so asto face the light guide 1.

The holder 8 has a face for retaining the optical filter 10 at the sidewhere the end portion of the light guide holder 7 is inserted. Theholder 8 has, on the opposite face thereto, a face for fixing the lightemitter mounting board 4 or 5. The holder 8 has an opening equivalent insize to the light emitter 2 on the face for fixing light emittermounting board 4. The face for retaining the optical filter 10 has anopening equivalent in size to the light guide 1. In addition, the holder8 has an opening equivalent in size to the light emitter 3 on the facefor fixing the light emitter mounting board 5. The face for retainingthe optical filter 10 has an opening equivalent in size to the lightguide 1.

In other words, when the light emitter 2 or 3 has sufficiently smallerarea than the area of the end surface of the light guide 1, the holder 8has a tapered structure. A portion corresponding to the open side of agroove portion of the light guide holder 7 as described below is shapedso as to project toward the light guide 1 side, compared to the otherportions.

The light guide holder 7 is formed of a thin plate, such as a metalplate, having a high light reflectivity, and has a groove portion 7 dformed as a long groove in the longitudinal direction. The light guide 1is disposed in the groove portion 7 d and retained therein in thelongitudinal direction. The open side of the groove portion 7 d is anexit portion for light to exit from the light guide 1.

The light guide holder 7 includes light guide retention holes 7 a to 7c. The light guide retention hole 7 a is formed on the bottom surfaceinside the long groove at the longitudinal central part. The light guideretention hole 7 b is formed on the inner surface at the open sidebetween the longitudinal central part and the longitudinal end. Thelight guide retention hole 7 c is formed on the inner surface at theopen side between the longitudinal central part and the longitudinal endopposite to the light guide retention hole 7 b.

The light guide holder 7 retains the light guide 1 at an appropriateposition with respect to the mirror 12 and the housing 6, and can returnleakage light from the side surface thereof and the rear side of thelight diverting surface 1 a back into the light guide 1. This eliminatesor reduces emission of unintended light from other than the exitportions 1 b and 1 c.

In addition, the light guide holder 7 is folded along the longitudinaldirection by hemming or the like, at the open side of the long groovethereof for retaining the light guide 1. This processing makes the cutsurface of the sheet metal less visible from the open side.

The housing 6 is formed of a sheet metal having a high workability suchas an iron material and aluminum material. Folding the plate-like memberinwardly at the locations illustrated by chain double-dashed lines inFIG. 30 forms a boat-shaped housing 6.

In other words, the plate-like member is folded inwardly at one longside of the rectangular bottom to form a long side wall portion. Theplate-like member is also folded inwardly at the other long side of thebottom so as to form a predetermined angle with respect to thetransverse direction of the bottom. In addition, the plate-like memberis folded inwardly at the short side of the bottom to form a short sidewall portion. The order of folding may be varied as appropriate. Suchfolding of the plate-like member forms the housing 6. The long side wallportion of the housing 6 is folded by hemming or the like, and thisprocessing makes the cut surface of the sheet metal less visible fromthe open side.

The housing 6 includes retention holes (light guide holder retentionholes) 6 a, 6 b and 6 c. The retention hole 6 a is formed on the bottomsurface at the longitudinal central part. The retention hole 6 b isformed on the bottom surface between the retention hole 6 a and the end.The retention hole 6 c is formed on the bottom surface between theretention hole 6 a and the end at the opposite side to the retentionhole 6 b side.

The housing 6 further includes an aperture 6 d formed on the bottomsurface along the longitudinal direction and an illumination devicemounting hole 6 e. The light guide holder 7 and the mirror 12 are thusfixed in the longitudinal, transverse, and vertical directions.

The retention hole 6 a is a round hole disposed on the bottom surface ofthe housing 6. The retention hole 6 a is disposed at the longitudinalcentral part between the aperture 6 d and a light guide holder retainer6 f in the transverse direction. Insertion of a pin 7 e of the lightguide holder 7 into the retention hole 6 a enables the position of thelight guide holder 7 to be fixed in the longitudinal and transversedirections.

The retention hole 6 b is a longitudinally elongated hole disposed onthe bottom surface of the housing 6. The retention hole 6 b is disposedat one longitudinal end between the aperture 6 d and the longitudinalside surface of the housing 6 in the transverse direction. Insertion ofa pin 7 f of the light guide holder 7 into the retention hole 6 benables the position of the light guide holder 7 to be fixed in thelongitudinal and transverse directions.

The retention hole 6 c is a longitudinally elongated hole disposed onthe bottom surface of the housing 6. The retention hole 6 c is providedat the other longitudinal end of the opposite side to the retention hole6 b side between the aperture 6 d and the longitudinal side surface ofthe housing 6 in the transverse direction. Insertion of a pin 7 g of thelight guide holder 7 into the retention hole 6 c enables the position ofthe light guide holder 7 to be fixed in the longitudinal and transversedirections.

The aperture 6 d is a hole formed along the longitudinal direction ofthe bottom surface of the housing 6. The aperture 6 d allows imageinformation of an object to be read (scattered light reflected by theobject irradiated with light) to be transmitted therethrough to animager (lens and image sensor), so that unnecessary light other than theimage information is eliminated or reduced.

The illumination device mounting holes 6 e are holes, provided at bothof the longitudinal ends of the bottom surface of the housing 6, forfixing the light source device to a reader device.

The mirror mounting surface 6 g is a member for retaining the mirror 12.The mirror mounting surface 6 g extends in the longitudinal directionand is provided transversely outside the aperture 6 d. The mirrormounting surface 6 g enables precise retention of the mirror 12 at anyangle.

If that the mirror mounting surface 6 g is provided so as to be directlycontinuous with the bottom surface of the housing 6, the mirror mountingsurface 6 g defining an angle for mounting the mirror 12 is too close tothe aperture 6 d, so that fabrication with sufficient precision becomesdifficult. The mirror mounting surface 6 g according to the presentembodiment is not provided so as to be directly continuous with thebottom surface of the housing 6, but is mounted on the surface foldedfrom the bottom surface of the housing 6. This thus enables the mirrormounting surface 6 g to retain the mirror 12 with precision.

The mirror mounting surface 6 g does not extend over the entire length,and a surface that is adjacent to the housing bottom surface, on whichthe mirror mounting surface 6 g is not provided, and is located at themirror mounting surface 6 g side with respect to the aperture 6 d, isfolded vertically from the housing bottom surface, thereby enhancing thestrength of the housing. The surface may be also folded in the directionopposite to the bottom surface to form a mount surface of the lightsource device. The mirror mounting surface 6 g has an area enough forthe mirror 12 not to sag; specifically, the optimal area and arrangementof the mirror mounting surface 6 g vary depending on the weight andstiffness of the mirror 12.

The fin 9 is fixed to the holder 8 together with the light emittermounting board 4 and a heat conductor 15 by inserting a screw 13 into aholder retention hole 6 j provided between the aperture 6 d and theillumination device mounting hole 6 e in the longitudinal direction ofthe housing 6, as illustrated in FIG. 29A. The light emitter mountingboard 4 may be fixed to the heat conductor 15 by, for example, glues,adhesives, or the like.

The light guide holder 7 is a member for retaining the light guide 1.The light guide holder 7 eliminates or reduces leaking of light emittedfrom the light emitters 2 and 3 and light exiting from the light guide 1to the outside of the light source device from unintended locations.

The light guide holder 7 is formed of a thin plate material and fixed tothe housing 6 by crimping, adhesive bonding, or the like. The lightguide holder 7 has a length less than the full length of the housing 6,and the light guide holder 7 and the holder 8 face their respective endsurfaces. The gap between the end surfaces in the lengthwise of thelight guide holder 7 and the holder 8 is sized greater than the extentof elongation of the light guide holder 7 due to its temperaturecharacteristics.

The light guide holder 7 has an opening that exposes the exit portions 1b and 1 c of the light guide 1. Both ends of the portions for retainingthe light guide 1 are inserted into the holder 8.

The heat conductor 15, which is a member for conducting heat, is made ofa material having high adhesivity and thermal conductivity, for example,a silicone sheet or the like. The heat conductor 15 is disposed betweenthe light emitter mounting board 4 and the fin 9 and between the lightemitter mounting board 5 and the fin 9.

The fin 9 and the housing 6 cool the light emitters 2 and 3.Specifically, heat generated by the light emitter 2 is conducted throughthe light emitter mounting board 4 to the heat conductor 15 and the fin9 and further to the housing 6 to be dissipated throughout the housing6. Heat generated by the light emitter 3 is conducted through the lightemitter mounting board 5 to the heat conductor 15 and the fin 9 andfurther to the housing 6 to be dissipated throughout the housing 6.

FIG. 31A is a diagram illustrating an optical path in the longitudinalcross section of the entire light source device according to the ninthembodiment. FIG. 31B is a diagram illustrating an optical path in thelongitudinal cross section of the vicinity of the end of the lightsource device according to the ninth embodiment. FIG. 32 is a diagramillustrating an optical path in the transverse cross section of thelight source device according to the ninth embodiment of the presentdisclosure.

A portion of incident light from the light emitters 2 and 3 to the lightguide 1 enters the light guide 1 directly, whereas the rest or a portionof the rest of incident light is scattered by the tapered portion of theholder inner wall and then enters the light guide 1, as indicated by anarrow in FIGS. 31A and 31B. Light entering the light guide 1 travelslongitudinally by repetitive reflection on the wall surface of the lightguide 1, and a portion of the light is incident on a white printedpattern or uneven shaped light diverting surface 1 a formed along thelongitudinal direction of the light guide 1.

Light not incident on the light diverting surface 1 a travelslongitudinally within the light guide 1 and exits from the end surfaceopposite to the entry surface. Light exiting from the end is scatteredby the tapered portion of the holder 8 and reenters the light guide 1.

Light incident on the light diverting surface 1 a is emitted byreflection from the exit portion 1 c facing the light diverting surface1 a in the direction of the irradiated part of the document mount aslinear secondary light 1 i extending longitudinally, as illustrated inFIG. 32.

A portion of the holder 8 corresponding to the open side of the grooveof the light guide holder 7 projects to the light guide 1 side, comparedto the other portions. Thus very little non-uniform light exits from thelight guide 1 at the end of the light guide 1.

On the other hand, a portion of light incident on the light divertingsurface 1 a exits from the exit portion 1 b to the mirror 12 as linearprimary light 1 h extending longitudinally. Primary light 1 h exiting tothe mirror 12 is reflected by the mirror 12 and exits in the directionof the irradiated part of the document mount as linear primary light 1 hextending longitudinally. In FIG. 32, which is a view of a cross sectionat the longitudinal central part, the arrows from the light divertingsurface 1 a of the light guide 1 toward the document mount each indicatea main optical path in which light reflected by the light divertingsurface 1 a reaches the object to be read.

The bifurcated linear light source device using the light guide 1according to the first embodiment is described in the ninth embodimentof the present disclosure. However, the bifurcated linear light sourcedevice may employ the light guide 1 according to any one of the secondto eighth embodiments, instead of the light guide 1 according to thefirst embodiment. In such a modified example, the light guide 1 isarranged in the bifurcated linear light source device such thatsecondary light 1 i exits toward the mirror 12, so that effects andadvantages similar to the present embodiment can be obtained.

Tenth Embodiment

A tenth embodiment of the present disclosure is described with referenceto FIGS. 33 to 36. An image reading device using a light guide 1according to the first embodiment is described in the tenth embodiment.

FIG. 33 is a view of a cross section perpendicular to a main scanningdirection (longitudinal direction), of an image reading device using animage sensor according to the tenth embodiment of the presentdisclosure. FIG. 34 is an exploded view of the image reading deviceaccording to the tenth embodiment of the present disclosure. FIG. 35 isan external view with a glass side up of the image reading deviceaccording to the tenth embodiment of the present disclosure. FIG. 36 isan external view with a signal processing board side up of the imagereading device according to the tenth embodiment of the presentdisclosure.

An object to be read (object to be irradiated) 17 is an object placedoutside an image sensor. The object to be read 17 is irradiated withexiting light for information of the surface to be read, and typicalexamples of such an object are paper sheets such as paper money,valuable papers, and checks. The object to be read 17 has, for example,reflected light information indicated by light reflected on the surfacethereof, transmitted light information regarding watermarks, or thelike.

The light guide 1 is a rod-shaped member formed of a transparent resinand extending in the longitudinal direction, as described in the firstembodiment. The light guide 1 has, along the entire longitudinal extent,the light diverting surface 1 a and the exit portions 1 b and 1 c havingthe curved surfaces. The light guide 1 emits linear light in twodirections by linear light emission from each of the exit portions 1 band 1 c.

A light guide 18 is a rod-shaped member formed of a transparent resinand extending in the longitudinal direction. The light guide 18 has,along the entire longitudinal extent, a light diverting surface 18 a andan exit portion having a curved surface. The light guide 18 emits linearlight in one direction by linear light emission from the exit portion.

The light guide 1 irradiates with secondary light 1 i the object to beread 17 that is disposed immediately above a rod lens array 21, that is,a read position to be irradiated, as illustrated in FIG. 33. The lightguide 1 irradiates a position outside (left side of the drawing) of theread position with primary light 1 h.

The light guide 18 irradiates with light the object to be read 17 thatis disposed immediately above the rod lens array 21, that is, the readposition.

The light emitter 2 a is a light source element such as an LED lightsource and is fixed on a light emitter mounting board 4 by soldering orthe like. The light emitter 2 a is driven with current by the lightemitter mounting board 4 to emit light. The light emitter 2 a emitsincident light that enters the light guide 1 from the end surfacethereof.

The light emitter 2 b is a light source element such as an LED lightsource and is fixed on a light emitter mounting board 4 by soldering orthe like. The light emitter 2 b is driven with current by the lightemitter mounting board 4 to emit light. The light emitter 2 b emitsincident light that enters the light guide 18 from the end surfacethereof.

A cover 23 and a transparent plate 22 have a conveying surface thereonalong which the object to be read 17 is conveyed, as illustrated in FIG.33. If equipment such as copying machines and banking terminalsincorporating the image reading device is equipped with one or both ofthe cover 23 and the transparent plate 22, then the image reading deviceaccording to the present disclosure may not have one or both of thecover 23 and the transparent plate 22.

The cover 23 is formed of a resin, metal, or the like and retains thetransparent plate 22. The transparent plate 22 is a transparentplate-like member made of a material such as glass and plastic and isfixed to the cover 23 by adhesion or the like. The cover 23 has, on theinner surface, claws for pressing the upper surfaces of the end portionsof the light guides 1 and 18, thereby fixing the light guides 1 and 18transversely and vertically.

A housing 6 is composed of a frame. The housing 6 has a portion forsupporting the cover 23 formed in the edge portion of one opening of thehousing 6 along at least the X-direction, as illustrated in FIG. 35. Thehousing 6 has a groove therein for retaining the rod lens array 21. Therod lens array 21 is fixed longitudinally, transversely, and verticallyto the housing 6 by adhesion or the like.

In addition, the housing 6 has, on the inner surface, claws for holdingthe lower surfaces of the end portions of the light guides 1 and 18, andfixing the light guides 1 and 18 transversely and vertically. Thehousing 6 retains the light guides 1 and 18, the rod lens array 21, thelight emitter mounting board 4, the cover 23, and a signal processingboard 19.

The rod lens array (imaging optical system) 21 extends longitudinallyand is fixed to the housing 6. The rod lens array 21 is disposed betweenthe light guides 1 and 18 in the transverse direction (the Y-axisdirection in FIG. 34 and the left-right direction in FIG. 37). The rodlens array 21 is disposed parallel to the light guides 1 and 18 in thelongitudinal direction (the X-axis direction in FIG. 34). The rod lensarray 21 images, on a sensor IC 20, light emitted from the light guides1 and 18 and reflected by the object to be read.

The sensor IC (light receiver) 20 is a solid state image sensor such asa CMOS and CCD. The sensor IC 20 is fixed on the signal processing board19 by die bonding or the like, and electrically connected to otherelements by wire bonding or the like. The sensor IC 20 is disposed so asto extend in parallel to the rod lens array 21. The sensor IC 20 isdriven by the signal processing board 19 and converts (photoelectricallyconverts) light information incident through the rod lens array 21 intoan electrical signal.

The signal processing board 19 is mechanically and electricallyconnected to the sensor IC 20 and fixes and drives the sensor IC 20. Thesignal processing board 19 is provided with a connector 24. The drivepower is supplied via the connector 24 to the signal processing board19. The signal processing board 19 transmits an electrical signal viathe connector 24. The signal processing board 19 drives the lightemitters 2 and 3 via the connector 24. The connector 24 is divided intomultiple sections depending upon the particular application (use forsensor driving, LED driving) and the like.

The signal processing board 19 has insertion holes 19 a, 19 b, and 19 c,as illustrated in FIG. 34. The signal processing board 19 is fixedlongitudinally, transversely, and vertically by fastening members suchas screws inserted into each of board mounting holes 19 d, 19 e, and 19f provided on the bottom of the housing 6. The insertion hole 19 a ofthe signal processing board 19 and the board mounting hole 19 d of thehousing 6 are provided on the same line in the vertical direction of thesensor IC 20 (the Z-axis direction in FIG. 34) and at the center of thesensor IC 20 in the longitudinal direction (the X-axis direction in FIG.34). The insertion holes 19 b and 19 c of the signal processing board 19and the board mounting holes 19 e and 19 f of the housing 6 are providedon the same line in the vertical direction of the sensor IC 20 (theZ-axis direction in FIG. 34) and in extension of the sensor IC 20 in thelongitudinal direction (the X-axis direction in FIG. 34). Providing thefastening portions (insertion holes 19 b and 19 c and board mountingholes 19 e and 190 in such locations enables the relative positionbetween the rod lens array 21 and the sensor IC 20 to be determined withhigh precision.

The light emitter mounting board 4, on which the light emitters 2 a and2 b are mounted, has a harness 26. The light emitter mounting board 4 isdisposed so that the surface opposite to the mount surface, on which thelight emitters 2 a and 2 b are mounted, is in contact with the lightsource board contact surface 6 m provided inside the housing 6 along themain scanning direction. The harness 26 passes through the insertionhole 19 a, 19 b, or 19 c of the housing 6 and is connected to theconnector 24 that is mounted on the signal processing board 19.

The rod lens array 21 is an example of imaging optical system forconverging light emitted from the light guides 1 and 18 and reflected bythe object to be read 17. The rod lens array 21 is an optical member;for example, a lens array for converging light on a line sensor (sensorarray) such as a rod lens array and macro-lens array, or a composite ofoptical members; for example, a lens or mirror constituting an imagesensor (image reading device) of a reduction optical system.

The tenth embodiment of the present disclosure is described with the rodlens array 21. The rod lens array is configured such that multiple erectunity magnification rod lenses are arranged in the main scanningdirection of the image sensor and fixed with a frame or the like. Forsimplicity, however, only a box-shaped contour elongated in the mainscanning direction is illustrated in the tenth embodiment of the presentdisclosure. In addition, the focal point of the rod lens array 21 isadjusted to be located on the surface on which the object to be read ispositioned (or the surface for conveying the object to be read, for acase in which the object to be read is conveyed).

The signal processing board 19 is a circuit board having a sensor IC 20mounted thereon and has a connector (not illustrated) to allow externalconnection. The sensor IC 20, which receives light converged by the rodlens array 21 and photoelectrically converts the received light, ismounted on the signal processing board 19 so as to be arranged onlyalong the reading length in the main scanning direction. In addition,the connector provides the electrical signal photoelectrically convertedby the sensor IC (sensor IC 20) of the signal processing board 19 to theoutside as an image signal.

The signal processing board 19 is fixed on the other opening surface ofthe housing 6 by fixing means such as screws. The fixing means are notlimited to screws, but may include pins, rivets, or the like. Inaddition, the other opening side of the housing 6 may also have astepped portion similar to the shorter inner length stepped portion ofthe one opening side of the housing 6 as described above, that is, theother opening side of the housing 6 also has a stepped portion having ashorter inner length. The signal processing board 19 may be fixed byfitting into the stepped portion. Another fixing means such as the abovedescribed screws and any other attachment may be employed.

Light entering the light guide 1 from the end surface thereof propagateswithin the light guide 1 longitudinally, and is reflected by the lightdiverting surface 1 a in a direction, for example, any of directionsperpendicular to the longitudinal direction, and exits as primary light1 h or secondary light 1 i. Light entering the light guide 18 from theend surface thereof propagates within the light guide 18 longitudinally,and is reflected by the light diverting surface 18 a in a direction, forexample, any of directions perpendicular to the longitudinal direction,and exits in the irradiation direction of secondary light 1 i of thelight guide 1. Secondary light 1 i from the light guide 1 and light fromthe light guide 18 are reflected by the object to be read 17 and aremade to converge by the rod lens array 21 to be imaged onto the sensorIC 20. Primary light 1 h from the light guide 1 irradiates an areadifferent from the area of the object to be read 17 irradiated withsecondary light 1 i and is transmitted through the object to be read 17.Use of the light guide 1 thus enables the image reading device toirradiate two different areas.

The tenth embodiment of the present disclosure is described for an imagereading device using the light guide 1 of the first embodiment. However,the image reading device may employ the light guide 1 according to anyone of the second to eighth embodiments, instead of the light guide 1according to the first embodiment. In such a modified example, the lightguide 1 is arranged in the image reading device such that primary lightand secondary light are emitted similarly to the light guide 1 accordingto the tenth embodiment, so that effects and advantages similar to thepresent embodiment can be obtained.

Eleventh Embodiment

An image reading device according to an eleventh embodiment of thepresent disclosure is described with reference to FIG. 37. An imagereading device using the light guide according to the first embodimentis described in the eleventh embodiment.

FIG. 37 is a view of a cross section perpendicular to a main scanningdirection, of an image reading device using an image sensor according tothe eleventh embodiment of the present disclosure. In FIG. 37, samereference signs denote the same or similar components to those in FIGS.32 and 33, and further descriptions thereof are omitted here.

Light entering a light guide 1 from the end surface thereof propagateswithin the light guide 1 longitudinally, and is reflected by the lightdiverting surface 1 a in a direction, for example, any one of directionsperpendicular to the longitudinal direction, and exits as primary light1 h or secondary light 1 i. An object to be read 17 is directlyirradiated with secondary light 1 i. Primary light 1 h is reflected by amirror 12, and the object to be read 17 is irradiated with the reflectedprimary light 1 h from the side opposite to secondary light 1 i sidewith respect to a rod lens array 21. Primary light 1 h and secondarylight 1 i exiting from the light guide 1 and irradiating the object tobe read 17 are reflected by the object to be read 17 and are made toconverge by the rod lens array 21 to be imaged on a sensor IC 20.

The present embodiment can provide the image reading device that enablesa single light guide 1 to irradiate the object to be read 17 with lightfrom two different directions.

The eleventh embodiment of the present disclosure is described for animage reading device using the light guide 1 according to the firstembodiment of the present disclosure, but the image reading device mayemploy the light guide 1 according to any one of the second to eighthembodiments of the present disclosure. Also in this case, the lightguide 1 is arranged in the image reading device such that primary lightand secondary light are emitted similarly to the light guide 1 accordingto the eleventh embodiment, so that effects and advantages similarthereto can be obtained.

Although the foregoing describes some example embodiments and modifiedexamples of the present disclosure, the present disclosure is notlimited thereto. The present disclosure has any appropriate combinationof the embodiments and modified examples, and modifications addedthereto as appropriate.

REFERENCE SIGNS LIST

-   -   1 Light guide    -   1 a Light diverting surface (reflecting portion)    -   1 b Exit portion (first exit portion)    -   1 c Exit portion (second exit portion)    -   1 d, 1 e, 1 f, 1 n, 1 r Side surface    -   1 g Entry surface    -   1 h Primary light (first exiting light)    -   1 h′ Optical path    -   1 i Secondary light (second exiting light)    -   1 k, 1 m Bottom surface (plane)    -   1L Light diverting surface (reflecting portion)    -   1 p, 1 q Notch (recess)    -   2, 2 a, 2 b, 3 Light emitter    -   4, 5 Light emitter mounting board    -   6 Housing    -   6 a, 6 b, 6 c Retention hole    -   6 d Aperture    -   6 e Illumination device mounting hole    -   6 f Light guide holder retainer    -   6 g Mirror mounting surface    -   6 j Holder retention hole    -   7 Light guide holder (light guide case)    -   7 a, 7 b, 7 c Light guide retention hole    -   7 d Groove portion    -   7 e, 7 f, 7 g Pin    -   8 Holder    -   9 Fin    -   10, 11 Optical filter    -   12 Mirror    -   13, 14 Screw    -   15 Heat conductor    -   16 Harness    -   17 Object to be read    -   18 Light guide    -   18 a Light diverting surface (reflecting portion)    -   19 Signal processing board    -   19 a, 19 b, 19 c Insertion hole    -   19 d, 19 e, 19 f Board mounting hole    -   20 Sensor IC    -   21 Rod lens array (imaging optical system)    -   22 Transparent plate    -   23 Cover    -   24 Connector    -   26 Harness    -   30 Light blocking member    -   110, 111 Circle of light guide 1

The invention claimed is:
 1. An image reading device, comprising: alight guide assembly including a light guide extending in a long axisdirection and having an end in the long axis direction from which lightenters the light guide, another light guide extending in the long axisdirection and having an end in the long axis direction from which lightenters the another light guide, an imaging optical system, and a housingretaining the light guide, the another light guide, and the imagingoptical system, wherein the light guide comprises a first exit facehaving a first curved surface having a convex cross sectionperpendicular to the long axis direction, and emitting first exitinglight, a second exit face having a second curved surface having a convexcross section perpendicular to the long axis direction, being connectedto the first exit face in a direction perpendicular to the long axisdirection, and emitting second exiting light in a direction differentfrom a direction of the first exiting light, a first reflecting facedisposed in a plane face facing the first exit face, and a secondreflecting face disposed in a plane face facing the second exit face,the second reflecting face having an area smaller than an area of thefirst reflecting face, the another light guide comprises a third exitface having a third curved surface having a convex cross sectionperpendicular to the long axis direction, and emitting third exitinglight, and a third reflecting face disposed in a plane face facing thethird exit face, wherein the second exiting light and the third exitinglight irradiate an area of the object different than an area irradiatedby the first exiting light, and the imaging optical system focusesscattered light from the object, the scattered light including thesecond exiting light and the third exiting light upon being reflected onthe object.
 2. The image reading device according to claim 1, wherein anoptical axis of the first exiting light and an optical axis of thesecond exiting light intersect with each other.
 3. The image readingdevice according to claim 1, wherein the first curved surface and thesecond curved surface have a same curvature.
 4. The image reading deviceaccording to claim 1, wherein the first curved surface and the secondcurved surface form a continuous surface.
 5. The image reading deviceaccording to claim 1, wherein the first curved surface and the secondcurved surface form a continuous surface, and the light guide forms, ina cross section perpendicular to the long axis direction, a shapeobtained by connecting straight lines to the first curved surface andthe second curved surface.
 6. The image reading device according toclaim 1, wherein the plane face facing the first exit face and the planeface facing the second exit face form, in a cross section perpendicularto the long axis direction, a shape obtained by connecting straightlines.
 7. The image reading device according to claim 1, the plane facefacing the first exit face and the plane face facing the second exitface have normals pointing in different directions.
 8. The image readingdevice according to claim 1, wherein the imaging optical system isdisposed between the light guide and the another light guide.
 9. Animage reading device, comprising: a light guide assembly including alight guide extending in a long axis direction and having an end in thelong axis direction from which light enters the light guide, anotherlight guide extending in the long axis direction and having an end inthe long axis direction from which light enters the another light guide,an imaging optical system, and a housing retaining the light guide, theanother light guide, and the imaging optical system, wherein the lightguide comprises a first exit face having a first curved surface having aconvex cross section perpendicular to the long axis direction, andemitting first exiting light, a second exit face having a second curvedsurface having a convex cross section perpendicular to the long axisdirection, being connected to the first exit face in a directionperpendicular to the long axis direction, and emitting second exitinglight in a direction different from a direction of the first exitinglight, a first reflecting face disposed in a plane face facing the firstexit face, and a second reflecting face disposed in a plane face facingthe second exit face, the another light guide comprises a third exitface having a third curved surface having a convex cross sectionperpendicular to the long axis direction, and emitting third exitinglight, and a third reflecting face disposed in a plane face facing thethird exit face, wherein the second exiting light and the third exitinglight irradiate an area of the object different than an area irradiatedby the first exiting light, and the imaging optical system focusesscattered light from the object, the scattered light including thesecond exiting light and the third exiting light upon being reflected onthe object.
 10. The image reading device according to claim 9, whereinthe plane face facing the first exit face and the plane face facing thesecond exit face have normals pointing in different directions, and theplane face facing the first exit face and the plane face facing thesecond exit face form, in a cross section perpendicular to the long axisdirection, a shape obtained by connecting straight lines.